1999 Fiscal Year Final Research Report Summary
ESTABLISHMENT OF COHERENT PHONON EXCITATION --as a new method for phase transition study--
| Project/Area Number |
10044050
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
YAGI Toshirou Hokkaido Univ., Res. Inst. Elec. Sci., Prof., 電子科学研究所, 教授 (30002132)
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| Co-Investigator(Kenkyū-buntansha) |
KASAHARA Masaru Hokkaido Univ., Res. Inst. Elec. Sci., Res. Assist., 電子科学研究所, 助手 (30001697)
TSUJIMI Yuhji Hokkaido Univ., Res. Inst. Elec. Sci., Asso. Prof., 電子科学研究所, 助教授 (20113673)
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| Project Period (FY) |
1998 – 1999
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| Keywords | femtosecond pulses / picosecond pulses / laser / phonon / phase transition / phonon excitation / ISRS / ISBS |
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| Research Abstract |
A new experimental method COHERENT PHONON EXCITATION, which is quite adequate for the study of phase transition has been established during the period of the present research project for two years from 1998 to 2000. This method provides a direct observation of the soft excitations closely related to the phase transition dynamics. The time dependence of the motion of the soft phonon mode and/or a relaxational mode are precisely distinguishable by their time dependence because the equation of motion of thoes excitation is usually driven in the time domain. As a result of the present project, a special improvement of the experimental system has been completed using an optical interference plate (phase mask) and heterodyne detection for the light diffracted from the excited phonons. The project is summarized as follows; 1. The soft ferroelectric BィイD22ィエD2 mode of KDP has been excited and observed its time dependence as a function of temperature in a range from RT to Tc. A clear single exponential time dependence of the BィイD22ィエD2 mode even 30 K far above Tc indicates an order-disorder type phase transition dynamics in KDP. 2. A precise observation of the dispersion relation of the phonon-polariton of the ferroelectric LiNbOィイD23ィエD2 has been done at room temperature. Because the present method has advantage in a small wave vector region, the dispersion relation of the AィイD21ィエD2 phonon-polariton is determined with high accuracy elucidating a very simple curve in contrast to the several resonance points below 7THz reported in the previous studies. 3. An ultra-slow relaxational motion in the glass-liquid transition has been studied with wave vectors defined precisely.
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